MANAGEMENT                                        PIH-107


            Controlling Rats and Mice in Swine Facilities

Robert M. Timm, University of Nebraska
Rex E. Marsh, University of California
Robert M. Corrigan, Purdue University
Ken Holscher, Iowa State University

Bob and Diane Bell, Camden, Arkansas
Peter T. Bromley, Virginia Polytechnic Institute and State University
William Fitzwater, Albuquerque, New Mexico
Mike and Debbie Nichols, Oakfield, Tennessee

     Rats and mice can be a major economic  threat  around  swine
facilities.   They  consume  and  contaminate feed and cause feed
losses through the gnawing of holes  in  feed  sacks  and  wooden
bins.  They  may also be responsible for maintaining or spreading
swine diseases.

     House mice (Mus musculus), Norway rats (Rattus  norvegicus),
and  roof rats (Rattus rattus) as a group are considered the most
troublesome and economically  important  rodents  in  the  United
States.  These  non-native  ``commensal''  rodents  live  under a
variety of urban and rural conditions. They  may  thrive  in  and
around  farms and rural homes and in some situations inhabit open
fields and agricultural crops.

     Norway rats will undermine building foundations and concrete
slabs.  Roof rats and house mice, in addition to Norway rats, are
particularly destructive  to  building  insulation.  Most  common
types  of insulation including rigid foam and fiberglass are sus-
ceptible to rodent damage. A rodent infestation can damage struc-
tures  by  thousands  of dollars in a matter of months. Addition-
ally, rodents may gnaw on  electrical  wiring  causing  equipment
malfunction,  power outages, and potentially dangerous short cir-

     Norway rats and house mice are found in all of the  contigu-
ous  48  states,  although the Norway rat may be absent from some
relatively large geographic areas of the West. The roof rat  pri-
marily occupies the coastal areas of Washington, Oregon, and Cal-
ifornia, as well as a larger area along  the  Gulf  and  Atlantic
coast  states from Texas to Maryland. In general, the roof rat is
considerably less important to the pork producer.

Rodents and Swine Diseases

     Rodents  and  other  wildlife  can  be  significant  in  the
transmission  of  swine  diseases.  The actual occurrence of such
diseases in rodents, and the degree to which they  contribute  to
disease problems on hog farms, is poorly documented.

     Table 1 lists swine diseases that rats and mice  may  harbor
or  disseminate.   Rodents, like other wild animals, insects, and
people, are capable of carrying diseases directly  into  a  swine
facility  upon  their entry. Rodents can spread or accelerate the
spread of established diseases from contaminated areas to  uncon-
taminated areas via their droppings, feet, fur, urine, saliva, or
blood.  As an example, Norway rats may  travel  through  infected
feces  of  isolated  sick  pigs and then contaminate the food and
water of healthy animals some several hundred feet away.

     Additionally, rodents  around  farm  buildings  are  a  food
source  that  may  attract  wild predatory animals such as foxes,
coyotes, raccoons, and skunks, which in turn  may  contribute  to
disease  problems.  Rodents  may also attract stray dogs and cats
which can transmit still other  diseases.  An  effective  disease
barrier  system  cannot  be  achieved  or maintained without good
|Table 1. Diseases of swine in North America that rodents may har- |
|bor or disseminate.                                               |
|                                                                  |
|_________________________________________________________________ |
|                                                  Rodents         |
|Disease                       Agent               implicated      |
|_________________________________________________________________ |
|Bordetellosis                 bacteria            rats            |
|Encephalomyocarditis          virus               rats, mice      |
|Leptospirosis                 bacteria            rats, mice      |
|Pseudorabies                  virus               rats*           |
|Salmonellosis                 bacteria            rats, mice      |
|Swine dysentery               bacteria            rats, mice      |
|Swine erysipelas              bacteria            rats            |
|Toxoplasmosis                 protozoan           various rodents |
|Trichinosis                   nematode            rats            |
|_________________________________________________________________ |
|                                                                  |
|* Opinions differ on the significance of rodents as the reservoir |

Recognizing Rodent Infestation

     Droppings, tracks, burrows, pathways,  and  fresh  gnawings,
including rodent-damaged feed sacks, indicate areas where rodents
are active. Rodent nests, made from fine shredded paper or  other
fibrous  material, are often found in sheltered locations. Around
swine facilities, insulated walls and ceilings are common nesting
locations  for rodents, especially mice. Rats utilize these areas
and also burrow into the  ground  inside  and  outside  of  swine
buildings.   When  present  in  relatively  high  numbers,  these
rodents occasionally can be seen during daylight hours, but  they
are  most  active  at  night, particularly just after dusk. Thus,
conducting an inspection of the premises at nightfall may  assist
in  identifying  the  location,  distribution,  and severity of a
rodent infestation.

Rat and Mouse Facts

     House mice are nondescript, brownish to greyish rodents with
relatively large ears and small eyes. They weigh about 1/2 oz. An
adult is about 51/2-71/2 in. long including the 3- to 4-in. tail.
Norway rats are large, robust animals whose fur color ranges from
reddish to greyish brown on  the  back  and  sides  and  grey  to
yellow-white  underneath. They are about 13-18 in. long including
the 6- to 81/2-in. tail. Average weight is about 11 oz., and  few
individuals  exceed  1  lb.  In  comparison,  the  roof  rat is a
smaller, sleeker rat usually colored blackish  to  grey,  with  a
grey  to whitish underside. A roof rat, in contrast to the Norway
rat, has a tail longer than its body and a  more  pointed  snout.
Also, its eyes and ears are relatively larger than the Norway's.

     Although commensal rodents often feed on cereal grains, they
will eat many kinds of food including garbage, insects, meat, and
even manure. House mice are sporadic feeders,  nibbling  bits  of
food  here  and  there, but often causing more economic loss from
gnawed feed sacks, contaminated feed, or from transmitted disease
than from actual food consumed. Rats tend to get their daily food
at one or two locations. Rats require  1/2-1  fl.  oz.  of  water
daily  (unless  feeding  on  moist or succulent foods), but house
mice can survive for long periods without liquid.

     Rats and mice have keen senses of taste, hearing, smell  and
touch. Roof rats, in particular, are excellent climbers and often
live on the second story of two-story farm buildings if  food  is
available. House mice and Norway rats will climb to reach food or
shelter, and all three rodent species can climb any rough  verti-
cal surface. They can run horizontally along wire cables or ropes
and can jump up 36 in. (12 in. for house  mice)  from  the  floor
onto a flat surface.

     These rodents have impressive capacities  for  reproduction,
which  makes  it  necessary to control them diligently and early,
before they reach populations that cause significant damage.  For
example,  in  a  single  year  a female house mouse may have 5-10
litters of usually 5 or 6 young each. Young are born  19-21  days
after mating, and they reach reproductive maturity in 6-10 weeks.
The life span of a mouse is usually 9-12 months. Norway and  roof
rats  are  only  slightly less fecund, with individuals typically
living 9-12 months but sometimes  longer.  Where  both  rats  and
house  mice  exist  on  the same premises, rats may exclude house
mice from their main areas of activity. Following the control  of
rats, mice may flourish.

Rodent Control

     Effective control involves (1) sanitation, (2)  rodent-proof
construction,  and  (3)  population  reduction. The first two are
useful as preventive measures.  When a rodent infestation already
exists,  population  reduction is almost always necessary. Reduc-
tion techniques include trapping, poisoning, and fumigation.

     Sanitation. Although good sanitation will  seldom  eliminate
rodents,  it  will certainly aid in controlling them. Conversely,
poor sanitation is sure to attract rodents  and  permit  them  to
thrive  in greater abundance. The continual presence of a sizable
rodent population suggests that too little attention is given  to
the  premises; often this goes hand-in-hand with poor sanitation.
Inadequate sanitation contributes to more  serious  rodent  prob-
lems,  but  rodent infestation (particularly house mice) does not
necessarily mean that sanitation is inadequate.

     On farms where feed grains are handled and stored, or  where
livestock  are  housed  and  fed,  it  is generally impossible to
exclude rodents from all  available  food.  In  such  situations,
removing  shelter  that  rodents  can use for hiding, resting and
nesting is valuable in control. Regular  removal  of  debris  and
control  of  weeds  around  structures  will reduce the amount of
shelter available  to  rodents.  Additionally,  a  clean,  3-foot
weed-free  perimeter around structures may make rodents feel more
``exposed'' and permits easier detection of rodent activity.

     Because mice can survive in very small  areas  with  limited
food  and  shelter,  it  is  almost  impossible to eliminate them
through sanitation alone, particularly on farms.  Most  buildings
in  which livestock feed is stored, handled, or used will support
a thriving population of house mice  if  not  mouse-proof.  Store
feeds  in  rodent-proof  buildings, rooms, or containers whenever
possible. Bins used for bulk feed should  be  kept  rodent-proof.
Stack  sacked feed on pallets with adequate space left around and
under stored articles to allow easy inspection  for  rodent  sign
and placement of traps or baits.

     Rodent-proof Construction. A lasting form of rodent  control
is  to  ``build  them  out''  by eliminating all openings through
which they can enter a structure.  Rodent-proof all places  where
feed is stored, processed, or used, if feasible.

     The paired front (incisor) teeth  of  rats  and  mice  curve
slightly inward.  This makes it difficult for them to gnaw into a
flat, hard surface. However, when given a  rough  surface  or  an
edge  to bite into, they can quickly gnaw into most materials. By
gnawing, rats can gain entry through any opening greater than 1/2
in.  across. Mice can enter a building through any opening larger
than 1/4 in. across. To prevent rodent entry, seal all such holes
with durable materials. Steel wool, packed tightly into openings,
is a good temporary plug.  To close  openings  or  protect  other
areas  subject  to gnawing, use materials such as those listed in
Table 2. Plastic sheeting or screen, wood, rubber, or other gnaw-
able  materials  are  not  adequate  for sealing openings used by
rodents.  Close openings around augers,  pipes  and  wires  where
they  enter  structures  with  portland cement mortar, masonry or
metal collars. Even a small unprotected opening can be an invita-
tion  to rodents. A common entry point for mice into buildings is
the unprotected end of metal siding. If not blocked with metal or
mortar,  these  openings  provide access into wall spaces and the
building interior. Rubber or  vinyl  weather  stops  are  quickly
gnawed  through. Design or modify buildings using metal siding so
these openings are not present.

     Doors, windows, and screens should fit tightly. It might  be
necessary  to  cover  the  edges  with  metal to prevent gnawing.
Depending on the age and type of building construction, it  might
not  pay  to  make  the  infested  building rodent-proof. In such
instances, give more attention to other techniques of rodent con-

     Rats can be discouraged from burrowing near building founda-
tions  by installing a strip of heavy gravel around their perime-
ter. Gravel should be at least 1 in. in diameter and  laid  in  a
band  at  least 2 ft. wide and 6 in.  deep.  Table 2. Recommended
materials for rodent proofing.

Material                  Thickness              Remarks
Concrete                  Minimum 2 in.          If reinforced.
                          Minimum 33/4 in.       If not reinforced.
Galvanized sheet metal    24 gauge or heavier    Perforated sheet metal
                                                 grills should be 14 gauge.
Brick                     33/4 in.               With joints filled with mortar.
Hardware cloth (wire mesh)19 gauge 1/2 x 1/2 in. To exclude rats.
                          24 gauge 1/4 x 1/4 in. To exclude mice.
Aluminum                  22 gauge               For frames and flashing.
                          20 gauge               For kick plates.
                          18 gauge               For guards.

     Trapping. Trapping is an effective way to  control  rodents.
House  mice  are  relatively  easy  to  trap,  but  trapping rats
requires more skill and labor. Trapping  is  the  method  to  try
first  where rodents are few, but it may be too time-consuming in
severe infestations. Trapping has  several  advantages:   (1)  it
does  not rely on potentially hazardous rodenticides; (2) it per-
mits the user to view his success; and (3) it allows for disposal
of  the  rodent carcasses, thereby eliminating dead animal odors,
which may occur when poisoning is done within buildings.

     The simple, inexpensive wood-based snap trap  is  effective.
Recently  new  and  improved  snap  traps  for rats and mice have
become available. These traps, made of sturdy plastic  or  metal,
are  easier  to set and effective when used correctly. Snap traps
are available through farm supply or  hardware  stores  and  from
pest  control  suppliers. Bait the traps with a mixture of peanut
butter and rolled oats or  with  a  small  piece  of  bacon  tied
securely  to the trigger.  Set them so that the trigger is sensi-
tive and will spring easily. Leaving traps baited but unset until
the  bait  has  been  taken  at  least once reduces the chance of
creating trap-shy rodents. Multiple-capture live traps for  mice,
such  as the Victor Tin CatO and the Ketch-AllO are effective and
will save service time. They, too, are available in some hardware
and feed stores as well as from pest control suppliers.

     Set traps close to walls, behind objects,  in  dark  corners
and  in places where rodent activity is evident. Tracking patches
of flour or fine sand can be used to determine where rodents  are
active.  Traps  may  be  placed on ledges or on top of pallets of
stored materials if mice or rats are active there.  Where  possi-
ble, place snap traps so that rodents will pass directly over the
trigger as they follow their natural course  of  travel,  usually
close  to  a  wall  (Figure  1).  Newer  snap traps have enlarged
triggers, but bait pans on older traps can be easily enlarged  so
that  rodents  are more likely to trigger the trap when traveling
over it. When set correctly, it is possible to catch rodents that
are not even attracted to the bait.

     Use enough traps to make the campaign  short  and  decisive.
Mice,  in  particular,  seldom venture far from their shelter and
food supply, so space snap traps no more than 10  feet  apart  in
areas  where  mice  are  active. When using snap traps, it may be
best to trap intensively for 2 or 3 weeks and then ``rest'' for a
couple  weeks  before  resuming efforts. This may save some labor
costs and helps prevent rodents from becoming ``trap-shy.'' Place
multiple  catch  traps  in  areas where mice seem especially per-
sistent and in areas of the building where mice  may  be  gaining
regular access (for example, on both sides of doorways).

     An alternative to traps are glue  boards,  which  catch  and
hold rodents attempting to cross them in much the same way flypa-
per catches flies. Place glue boards along  walls  where  rodents
travel.  Because  they  stick tenaciously to any object coming in
contact with them, do not use them where children, pets or desir-
able  wildlife have access to them. Glue boards lose their effec-
tiveness in dusty areas unless covered, and extremes of  tempera-
ture  also  may  affect  their  tackiness.  The glue board can be
placed inside a suitable cardboard box with appropriate holes cut
for  the  rodents  to  enter. This also aides in disposal of car-
casses. Glue boards are generally more  effective  for  capturing
mice than rats.

     Using Poison Baits (Rodenticides).  Both  anticoagulant  and
non-anticoagulant  rodenticides  (rodent  poisons) are available.
Although ready-to-use baits come in a wide variety of types, some
persons  highly  knowledgeable  in  rodent  control prefer to mix
their own baits using rodenticide concentrates.  In  most  situa-
tions,  ready-to-use  commercial baits are preferred because they
have proven efficacy and do not require that the applicator  han-
dle the concentrated toxicant, which is more hazardous.

Table 3. Non-anticoagulant rodenticides and some  of  their  useful
characteristics for controlling rats and mice in swine facilities.
                                        a.i.* in                             
                                        food    Mode of          Time to     
Common name    Chemical name            bait    action           death       
bromethalin    N-methyl-2,4-dinitro-    0.01    CNS depression   2-4 days    
(AssaultO      N-(2,4,6-tribromophenyl)-        and paralysis                
VengeanceO)    6-trifluoromethyl)
cholecalciferol9,10-Seocholesta-5,7,    0.075   Mobilizes cal-   3-4 days    
(QuintoxO      10(19)-trein-3-betaol            cium resulting               
RampageO)                                       in death from
red squill     scilliroside             10.0    Heart paralysis  < 24 hrs.   
strychnine     strychnine               0.25-1  Tetanic convul-  1/4-3 hrs.  
                                                sions leading                
                                                to respiratory
zinc phosphide zinc phosphide           1.0-2   Phosphine gas    1/2-20 hrs.
                                                enters circu-                
                                                latory system;
                                                heart paralysis,
                                                and liver damage

Table 3. (Continue..)
                                            Rodents controlled
                Bait ac-Bait    Human Swine House Norway Roof
Common name     ceptanceshyness hazardhazard mice  rats  rats
bromethalin       good    none   mod   unk   yes    yes   yes
(AssaultO               reported
cholecalciferol  fair-    none   low-  unk   yes    yes   yes
(QuintoxO         good  reported mod
red squill       poor-    mod-   low   low    no    yes   no
                  fair    high
strychnine        fair    mod-   mod-  mod   yes    no    no
                          high   high
zinc phosphide    fair    mod-   mod   mod   yes    yes   yes
* Active ingredient.
** Principal active ingredient.
NOTE: Rodenticides such as ANTU, arsenic trioxide,  and  phosphorus
are  registered  and  available  in  some states, although they are
rarely used today because of their  limited  availability  and  low
efficacy  in most situations. Both arsenic and phosphorus are quite
toxic to swine and in some countries  have  been  used  to  control
feral pigs.

     Some non-anticoagulant rodenticides (Table 3)  will  give  a
quicker  knockdown of a rodent population than anticoagulants, as
they are effective with a single feeding and are relatively rapid
in  action.  They  may be preferred where rodents are abundant or
where it is difficult to get them to accept a  bait  for  several
days in succession (as may be necessary with some anticoagulants)
because of competing food items.

     With  most  non-anticoagulant  rodenticides,  ``prebaiting''
with  poison-free bait for several days before the rodenticide is
offered will increase bait acceptance, thereby increasing control
success.  Because  ``bait  shyness''  or  ``poison  shyness'' may
develop following  a  sublethal  ingestion  of  some  single-dose
rodenticides such as zinc phosphide or red squill, it is best not
to use these more than twice a year  at  a  given  location,  and
preferably only once.  Because non-anticoagulant rodenticides are
generally more rapid in action and because first  aid  and  anti-
dotes  are often less effective, some of these materials are more
hazardous to humans, pets, or livestock if accidentally ingested.
Table 4. Anticoagulant rodenticides for controlling rats  and  mice
in  swine  facilities.  All  anticoagulants  have  the same mode of
action and all have a delayed time  to  death,  although  some  act
slightly  faster  than  others.  All  anticoagulants  are effective
against house mice, Norway rats, and roof rats. They all  are  con-
sidered  to  have  good bait acceptance, no bait shyness, low human
hazard, and moderate-to-high hazard to swine.

                                                           a.i.* in
Common name       Chemical name                            bait
brodifacoum**     3-{3-[4'-bromo(1,1'-biphenyl)-           0.005
(HavocO           4-yl]-1,2,3,4-tetrahydro-1-
TalonO)           naphthalenyl}-4-hydroxy-2H-1-
bromadiolone**    3-{3-[4'-bromo(1,1'-biphenyl)-           0.005
(MakiO            4-y1]-3-hydroxy-1-phenylpropyl}-
ContracO)         4-hydroxy-2H-1-benzopyran-2-one
chlorophacinone   2-{(p-chlorophenyl) penylacetyl}-        0.005
(RoZolO)          1,3-indandione
diphacinone       2-diphenylacetyl-1,3-indandione          0.005
coumafuryl        3-(a-acetonylfurfuryl)-4-                0.025
(FumarinO)        hydroxycoumarin
(PivalO)          2-pivalyl-1,3-indandione                 0.025
ValoneO           2-isovaleryl-1,3-indandione              0.055
ProlinO           3-(a-acetonylbenzyl)-4-hydroxycoumarin   0.025
                  + sulfaquinoxaline (0.025%)
warfarin          3-(a-acetonylbenzyl)-4-hydroxycoumarin   0.025

* Active ingredient.
** Effective on anticoagulant (warfarin)-resistant rats and mice.

     Anticoagulant rodenticides (Table 4) cause death by internal
bleeding,  which  occurs as the animal's blood loses its clotting
ability and capillaries are destroyed. The active ingredients are
used  at  very  low  levels, and bait shyness does not occur pri-
marily because of their slow action.

     Most anticoagulant baits cause death  only  after  they  are
eaten  for  several  days. Brodifacoum and bromadiolone baits are
exceptions, as these rodenticides can  cause  death  following  a
single  feeding,  although  the  rodent  may continue to feed for
several  days.  All  anticoagulant  rodenticides  are  relatively
slow-acting,  and  death usually occurs 3 to 5 days following the
ingestion of a lethal amount.

     When multiple-dose anticoagulant rodenticides are used, bait
must  be  available  continuously until all rodents stop feeding.
This usually takes at least two weeks.  Complete  elimination  of
rodents  is  often possible with anticoagulant rodenticides. This
is more rarely the case with non-anticoagulant  rodenticides  and
hence  the  anticoagulants  are often used as a followup to other
types of control.

     Occasionally populations of rodents develop which are resis-
tant  to  the  multiple-dose  anticoagulants. This usually occurs
following long, continual use of these products. Such rodents can
be controlled by using the single-dose anticoagulants brodifacoum
or bromadiolone or by using one of the non-anticoagulants.

     Bait Selection and Placement. Rodent baits are available  in
several  forms.  Grain baits in a loose meal or pelleted form are
available in small plastic, cellophane, or paper  packets.  These
sealed  ``place packs'' keep bait fresh and permit easy placement
of the baits into burrows, walls,  or  other  locations.  Rodents
gnaw into the packet to feed on the bait.

     Anticoagulant baits formulated into paraffin blocks are use-
ful  in  damp  locations  where  loose  grain  baits  would spoil
quickly. Take care to avoid placing them in locations where  they
could be reached and fed on by pigs.

     A particularly good bait material for house mice  is  canar-
ygrass  seed.  In  many  situations, mice prefer such bait to hog
feed or other cereal grains.  Where ample feed  is  available  to
rodents,  control  can  be  improved  by  using baits prepared of
highly-preferred  foods.  Likewise,  those  anticoagulant  baits,
which are lethal in a single feeding, are more effective in these

     Where water is scarce or absent, water or food items of high
water  content  are often preferred to dry baits. Some anticoagu-
lant rodenticide concentrates are available to  be  dissolved  in
water  to  make  a  liquid  bait. Even though mice require little
water to survive, they will quickly accept available water baits.
When  the  water  sources  of  rats can be reduced or eliminated,
liquid baits will provide excellent  control.  Liquid  baits  can
also supplement cereal baits, resulting in better control.

     Important!  Proper  placement  of  baits  and  the  distance
between  placements is important for successful control. Baits or
traps must be located where rodents are living.  Place  baits  or
traps  as close to their shelter as the rodent's alternative food
resources. For house mice, space bait placements no farther  than
10  ft.  apart  (preferably  6-8  ft.)  in  areas  where mice are
present. Since rats will travel farther to  feed,  baits  can  be
spaced  25-50  ft.  apart. But whenever possible, place rat baits
directly into, or very close to, rat burrows.

     Bait boxes or stations  provide  a  secluded  feeding  area,
holding  ample  multiple-dose, anticoagulant bait for the rodents
in that area. Bait  boxes  protect  the  bait  from  weather  and
exclude  pets  and other nontarget animals.  Bait stations should
be large enough to accommodate several rodents at  one  time  and
should have at least two rodent-size openings (11/2 in. for mice;
21/2 in. for rats). Place bait boxes  next  to  walls  (with  the
openings  close to the wall), or near burrows and in other places
where rodents are active.  Clearly  label  all  bait  boxes  with
``Rodent  Bait  Do Not Touch'' or other appropriate warnings as a
safety precaution. To prevent bait boxes from being tipped  over,
fasten  them  to  the floor or wall (Figure 2). Where young chil-
dren, pets, or livestock may  be  present,  secure  the  lids  to
prevent  unwanted  access  to  the bait. Two designs for homemade
bait  stations  are  shown  in  Figure  3.  Some  of  the  newer,
``tamper-proof'' bait stations available from pest control supply
distributors are more durable  and  will  hold  up  inside  swine
structures better than light plastic or cardboard stations.

     Fumigants. Fumigants are commonly  used  to  control  Norway
rats  in  their  burrows in outdoor situations. Compounds such as
carbon monoxide (gas cartridges) and aluminum phosphide have been
used  to  fumigate rat burrows.  Fumigation of house mice is usu-
ally limited to situations where  they  occur  inside  structures
such  as  grain bins or warehouses. Caution! Fumigants are highly
toxic to people and animals, and must not be used in  any  situa-
tion  that  might expose people or domestic animals to the gases.
Because of inherent potential  hazards  with  fumigants  such  as
chloropicrin  and  methyl  bromide, only licensed structural pest
control operators should use fumigants in any situation involving
buildings or other structural enclosures.

     Maintaining Control. Once ``control'' is achieved, some pork
producers tend to let their guard down and not pay much attention
to rodent control for a couple  of  months.  Unfortunately,  this
habit  leads  to  ``undoing'' all the work it took to control the
rodents initially. Keep in mind that a few rodents are likely  to
survive  even the most thorough control effort. And, rodents from
nearby fields or structures may invade swine  facilities  at  any
time.  These  rodents  will multiply quickly if not kept in check
with an ongoing control program. Therefore, it  is  important  to
establish  permanent  bait stations in buildings and around their
perimeters. Fresh anticoagulant bait in these stations will  con-
trol  invading  rodents  before breeding populations become esta-

     Rodent control should be a regular and continual part  of  a
pork  production  operation. Make it a point to put aside an hour
or two each month after control has been achieved  to  check  and
refill  bait  stations  and  inspect  facilities for fresh rodent
signs. Mark it on the calendar.

     Safety  Precautions.  Certain  general  safety   precautions
should  be  followed in addition to those appearing on the labels
of products. Consider all rodenticides dangerous enough to  cause
death  to  pigs,  and  place  baits where only rodents can get to
them. All known rodenticides present some  degree  of  hazard  to
animals   besides  rodents.  The  anticoagulants  and  some  non-
anticoagulant rodenticides may present some hazard  to  predators
or  scavengers  which  feed on the carcasses of poisoned rodents.
Therefore, take care to keep baits out of the reach  of  domestic
animals or nontarget wildlife. Remember that hogs will often feed
on rodent carcasses. Handle rodent carcasses with rubber  gloves,
long  tongs,  or  newspaper,  and  bury  or  incinerate  all dead
rodents. As an added safety precaution, keep dogs  or  cats  con-
fined or well-fed while baiting operations are in progress.

     Label  all  bait  containers  and  stations   clearly   with
appropriate  warnings,  and keep unused bait in its original con-
tainer. Store bait and concentrates in a locked  cabinet  out  of
the  reach  of children or animals, and post appropriate warnings
on the outside of cabinet doors. If baits are stored  with  other
chemicals,  be sure that they are packaged in airtight containers
to prevent absorption  of  foreign  chemical  odors,  which  will
reduce  the  bait's  effectiveness. Carefully follow label direc-
tions on all rodenticides. Except when using permanent bait  sta-
tions,  remove  and  destroy  all  uneaten bait at the end of the
poisoning program.

     Sound and Electronic Devices. Although  rodents  are  easily
frightened  by  strange  or  unfamiliar noises, they quickly grow
accustomed to regularly repeated sounds and thus  live  in  grain
mills  and  factories  with high sound levels. Ultrasonic sounds,
those above the range of human hearing, have very limited use  in
rodent  control because they are directional and do not penetrate
behind objects. Also, they lose their intensity quickly with dis-
tance. There is little evidence that sound of any type will drive
established mice or rats from buildings.

     Predators. Although cats, dogs and other predators may  kill
rodents,  they  do  not  give  effective  control  in  most  cir-
cumstances. It is common to find rodents  living  in  very  close
association  with dogs and cats. Mice and rats may obtain much of
their diet from the pet's dish or from what pets spill.


     1. Try to eliminate or reduce the number of  places  rodents
can  use for shelter. Prevent clutter in and around buildings and
structures, and keep  stored  feed  in  rodent-proof  facilities.
Where  practical, make structures rodent-proof. When rodents have
no place to hide or nest, they cannot thrive.

     2. If rodents or rodent signs  are  present,  begin  control
efforts. Use traps or rodenticides to reduce their numbers. Place
baits or traps in areas where rodents are  active,  and  maintain
control efforts diligently until successful.

     3. Once rodent numbers have been reduced, continue a regular
program  of control to keep rodent numbers to a minimum. Maintain
permanent bait stations or traps to control invading rodents  and
to keep surviving rodents from multiplying.

     To simplify information, trade names of some  products  have
been  used.  No endorsement of named products is intended, nor is
criticism implied to similar products not mentioned.

NEW 1/87 (5M)

Figure 1. Right and wrong placement for snap traps.
Figure 2. A rodent bait box attached to the top of a pen dividing
          wall in a swine facility. When used in such locations,
          bait boxes must be securely fastened and out of pigs'  
Figure 3 (a). A homemade rodent bait station can contain liquid
              as well as solid (cereal) baits.
Figure 3 (b). A safe, effective homemade baiting station.

Cooperative Extension Work in  Agriculture  and  Home  Economics,
State  of Indiana, Purdue University and U.S. Department of Agri-
culture Cooperating. H.A. Wadsworth,  Director,  West  Lafayette,
IN. Issued in furtherance of the Acts of May 8 and June 30, 1914.
It is the policy of the Cooperative Extension Service  of  Purdue
University  that  all  persons  shall  have equal opportunity and
             access to our programs and facilities.